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Carbonated water compatabiliy question

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Dr. Slack

Fri Dec 15 2006, 11:09AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

My family, at least my wife and middle son, get through vast quantities of carbonated water. Now it's not particularly expensive in the local shop, but it does require a lot of hauling back to the house, and the tantrums when we run out have to be heard to be believed.

So my Christmas holiday project (unbeknown to them) is an in-line, automatic, carbonater. The general idea is a 2litre fizzy pop bottle gets connected to mains water and a CO2 (sodastream) cylinder via valves. I've got the level sensing, pressure sensing, CO2 injection, and general water/power and gas explosion safety sorted, but I have a question about the pipe and valve materials.

A solution of CO2 in water is weakly acid. Much of the plumbing and valves will be submerged in this stuff 24/7, and I need to water to remain safe and not disolve out nasties. Can I use copper/brass compression fittings, I suspect so as they are generally compatible? I am disinclined to use lead-bearing solder fittings, but is lead free OK, being in contact with copper under weak acid? I would expect plastic plumbing would be OK as the bottle is not goin above 1 bar. Taking my lead from the food industry, stainless would be ideal, but it's a tad expensive as I would have to buy stuff new.

Any thoughts?

Bored Chemist

Sun Dec 17 2006, 02:35PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

I can't say I have ever tried this sort of thing, but I know that having different metals in contact under water (especially impure water) is unhelpful in terms of reducing corrosion. The best advice I can give is to use as few metals as possible. Brass is usually OK with copper and solder should be no problem but I'd still avoid it as far as possible, Whatever the manufacturers tell you about lead free solder, it simply hasn't been as well tested as the old stuff. (That doesn't mean I recommend the lead based stuff).
The other thing I would make very sure of is that the water can't suck back into the CO2 cylinder- not a major risk but it needs thinking about.
One possible source of information is the local pub where they pump similar materials around and have the experience of how to do it safely. (If nothing else, its an excuse to go to the pub

Billybobjoe

Mon Dec 18 2006, 02:17AM

Registered Member #396 Joined: Wed Apr 19 2006, 12:55AM
Location: Pittsburgh, PA
Posts: 176

From

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"Note that the only components that contact the liquid beverage are the bottle, bottle cap, and the stainless steel fitting. Most brass is an alloy that contains a few percent of lead for machinability. Mild carbonic acid (carbonated water) does corrode brass when left in contact for long periods. I don't myself have the slightest concern that one would be exposed to any lead from using brass in this way, but if you like to be certain, then the stainless steel fitting is the thing to have. Commercial soft drink apparatus is all stainless steel and plastic wherever it contacts carbonated beverages; this is important because the slightly-acidic soda is in constant contact with the metal."

He is not concerned because his method of carbonating involves a fitting in the cap of a bottle, which s then saken under pressure. With your system, like you said, the carbonic acid solution will be sitting in the fittings. Personally, if it was me, seeing as how much of this stuff you consume, I would not use brass. Go with plastic, stainless, or aluminum, for your family's sake (esp. for children, as lead accumulates in the body over time). I would think that copper would be OK (probably the best taking into consideration price and safety) also, using lead free solder, as that is used in numerous potable water applications.

Dr. Slack

Fri Dec 22 2006, 06:42PM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

Thanks for those. On reflection, I may well put the bottle the right way up, with a plastic tube to the bottom. This means continuous immersion only for plastic componentns. I find I'm able to replace solder with hot melt glue, certainly at these low pressures anyway.

ConKbot of Doom

Sat Feb 10 2007, 08:11AM

Registered Member #509 Joined: Sat Feb 10 2007, 07:02AM
Location:
Posts: 329

Bored Chemist wrote ...

I can't say I have ever tried this sort of thing, but I know that having different metals in contact under water (especially impure water) is unhelpful in terms of reducing corrosion. The best advice I can give is to use as few metals as possible. Brass is usually OK with copper and solder should be no problem but I'd still avoid it as far as possible, Whatever the manufacturers tell you about lead free solder, it simply hasn't been as well tested as the old stuff. (That doesn't mean I recommend the lead based stuff).
The other thing I would make very sure of is that the water can't suck back into the CO2 cylinder- not a major risk but it needs thinking about.
One possible source of information is the local pub where they pump similar materials around and have the experience of how to do it safely. (If nothing else, its an excuse to go to the pub

I know that new lead-free solder is being implemented with electronics with ROHS and similar... but when it comes to plumbing, lead free solder has been around for years. Or did you in fact mean lead-free plumbing solder?

Bored Chemist

Sat Feb 10 2007, 01:55PM

Registered Member #193 Joined: Fri Feb 17 2006, 07:04AM
Location: sheffield
Posts: 1022

"lead free solder has been around for years"
And the lead bsaed stuff has been around fo millennia.

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